The invention relates to a liquid filter which is combined with a cooler for the liquid being filtered, and which contains a valve stem with a gasket for closing openings which are intended to facilitate draining the filter housing during an oil change. The invention furthermore relates to a cooler which is suitable for installation in this filter-cooler combination.
A filter with valve stem for closing a drain opening is disclosed, for example, in EP 612 549 B1. If one consults FIG. 2, for example, of this document, the principle of the operation of the valve stem will be apparent from the example of its installation. A filter element 16 is installed upright in a pot-like or cylindrical housing 1. The cylindrical housing is closed by a screw cover 2, a valve stem 3 being integrated into the cover and sealing at its end an opening for draining any oil remaining in the filter when the filter cartridge is removed. This opening is released whenever the screw cover 2 is opened, since the valve stem is positively guided axially by the screw cover 2. In this manner a thorough draining of the filter housing can be achieved, and lubricating oil is prevented from passing into the environment when the filter is changed. Also, the total draining permits a complete oil change, which is advantageous since residues would bring contaminants into the fresh oil from the outset.
If a filter system of the kind described is combined with a cooler for the liquid being filtered, it is desirable also to drain the oil cooler. Unlike the filter element, however, the oil cooler has a complex geometry, so that a certain amount of residual oil always remains therein. It cannot in this case be removed by using the valve stem to uncover a drain hole in the bottom of the housing, because residual oil will still remain in the cooler element itself.
It is the object of the present invention to provide an improved liquid filter with a cooler.
It is also an object of the invention to provide a liquid filter with a cooler which assures a thorough drainage of the old oil before an oil change.
Yet another object of the invention is to provide an improved cooler for use with a liquid filter.
These and other objects are achieved in accordance with the present invention by providing a liquid filter comprising a cylindrical housing having an upwardly oriented opening, relative to gravity, and a threaded cover screwed onto the housing to close the opening, the housing having a filter inlet and a filter outlet for a liquid to be filtered, a filter cartridge sealingly disposed in the housing between the inlet and outlet so that liquid from the inlet must pass through the filter cartridge to reach the filter outlet, a cooler disposed underneath the filter cartridge in the housing such that liquid which has passed through the filter cartridge can flow through the cooler to the filter outlet, the cooler having an outlet opening, a valve stem extending along the axis of rotation of the threaded cover, the valve stem having a range of axial play relative to the threaded cover which is limited by the threaded cover, and at least one seal on the valve stem which seals the cooler outlet opening, the outlet opening being opened by unscrewing the threaded cover from the housing.
In accordance with a further aspect of the invention, the objects are achieved by providing a cooler for installation in a liquid filter as describe above in which the cooler has a drain outlet opening which is closed when the cooler is installed in the liquid filter and the threaded cover is screwed onto the filter housing.
The liquid container according to the invention has a pot-like or cylindrical housing whose opening points upward with respect to the force of gravity. The cylinder does not need to be oriented precisely vertical; instead it may be inclined at an angle to the vertical. A filter cartridge is installed in the cylindrical housing through which the liquid to be filtered can flow from a filter inlet to a filter outlet. A cooler is disposed beneath the filter cartridge. It has an entry for the filtered liquid, which communicates with the clean side of the filter cartridge. This can be achieved by also installing the cooler in the cylindrical housing of the filter and having it communicate through gaskets with the appropriate connections. Another possibility is to arrange the cooler under the filter housing, in which case the housing as well as the cooler must have connections communicating one with the other. These connections must assure the circulation of the liquid through the filter cartridge and cooler, and provide for the circulation of a coolant in the cooler. In both situations, however, the cooler has a drain opening which is closed by a gasket. This gasket is applied to a valve stem, which is connected to the screw cap of the housing such that its axial play is limited by this connection. A defined axial play can be provided, which also includes the case where the axial free play equals zero. To attach the valve stem to the screw cover, a catch or snap fastener, for example, can be provided, which permits a certain axial free play. Another possibility is to attach the valve stem permanently to the screw cover, for example by adhesively bonding the valve stem to the cover, or even to manufacture the valve stem in one piece with the screw cover.
In any case, the result of the axial fastening of the valve stem to the screw cover is that, when the cover is unscrewed, the gasket is moved away from the drain opening in the cooler. The drain opening is located on the cooler such as to promote its drainage. If this cooler is used, for example, for the lubricating oil circuit of an internal combustion engine, when the oil is changed, the cooler can be completely or at least largely emptied by means of the drain opening, so that the fresh oil is not immediately contaminated by residues of the used oil. In this way longer engine service life can be achieved, as well as longer intervals between oil changes, so that the reliability of operation of the internal combustion engine increases, and greater economy in the operation of the internal combustion engine is achieved.
During the operation of the cooler, the seal or gasket effectively prevents any bypassing of the cooler passages, which would reduce its cooling efficiency. Since the cooler has no filtering function, however, perfect sealing is not necessary, and a slight residual leakage may be technically acceptable. Therefore the gasket does not need to satisfy any stringent requirements. The gasket can be made from an elastomer, but it is also possible to create it by an appropriate geometrical configuration of the valve stem.
In accordance with another embodiment of the invention, the valve stem has an additional gasket which sealingly closes a drain opening in the housing. Thus the drain opening is likewise opened by the removal of the screw cover and can promote the drainage of the entire filter housing. At the same time the drain opening can also be used to carry out of the housing the liquid issuing from the cooler.
One particular preferred embodiment envisions a center tube provided in the cooler and the drain opening is provided in this central tube. The valve stem can then extend into this central tube and seal the drain opening there. If the cooler a plate type cooler, the center tube has additional advantages during manufacturing. It passes through the individual plates and is soldered to them in order to create spaces in the cooler for the liquid being cooled as well as for the cooling liquid.
The central tube as well as the valve stem must be arranged in the axis of rotation of the screw cover. This assures that the rotation of the screw cover will not cause any collision of the valve stem with parts in the interior of the filter housing. By rotating the screw cover, the necessary axial displacement of the valve stem is achieved, which results in the opening of the drain.
Another possibility is to provide the drain opening in the bottom plate of the cooler. In this case, however, the cooler must be inserted as a component into the housing, while at the same time an intermediate passage is formed which is constituted partly by the bottom plate of the cooler and partly by the wall of the housing. The drain opening of the cooler leads into this passage, so that opening it permits the liquid residue to be removed from the cooler. The intermediate passage must have a connection either to the outlet or to the drainage opening in the filter housing. With this arrangement an especially fast removal of the liquid from the cooler can be achieved.
In accordance with another embodiment of the invention, the valve stem is fastened to a support tube which accommodates the filter cartridge. The support tube must then be fastened in turn to the screw cover in order thereby to limit the axial play of the valve stem. The filter cartridge is fastened on this support tube. This is preferably accomplished by placing the filter cartridge with at least one end plate onto the support tube. The valve stem can be fastened on the support tube with an appropriate means, such as a catch or snap fastener or by adhesive bonding. The support tube and valve stem, however, can also be manufactured in one piece. The advantage of this arrangement consists in a material saving, since the valve stem does not have to be guided all the way to the screw cover. The support tube is a component which has to be provided anyway due to the design.
An additional advantageous embodiment is obtained by providing a coupling device between the filter cartridge and the cooler to join these two components sealingly together. The liquid can thus be conveyed from the clean side of the filter cartridge directly to an inlet in the cooler. Advantageously, this coupling device is designed so that the filter cartridge can be placed with its end plate in sealing engagement with the coupling device, e.g. with a tubular stub on the sealing device. In this way a seal is simultaneously assured, since the end plate yields elastically. The other end of the coupling device preferably is disposed on the top plate of the cooler, which simultaneously contains the inlet for the liquid to be cooled. In this manner the different filter cartridges can be fitted to the cooler by modifying only a single component. This has an advantageous influence on the cost of production of a series of filters.
A cooler according to the invention is suitable for cooperating with the liquid filter described above. This can be done either by installing it in the filter housing or by building it onto the latter. In the second mode of installation it is necessary to assure that the valve stem can reach from the cylindrical housing into the attached oil cooler. Also, it it is necessary to assure that the liquid running out of the cooler can either be collected or can be fed to the liquid circuit. To be able to be built into the system according to the invention, the cooler requires the outlet opening already described.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either individually or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.